Unmountable Boot Volume Error On Clean Install

The laptop was running slow and I decided it was time to clean things up and get her running like new again. Backed up everything and wiped the drive using KillDisk. Three and a half hours later when the process was done I popped in my Wndows 7 OEM disc only to be greeted with the dreaded Unmountable Boot Volume on that pretty blue screen.  Tried several times but it’s the same thing each time. What did I screw up? Appreciate any help. Thank you!
(Dell XPS 15, Western Digital 750GB hard drive)

It looks like you killed your disk with KillDisk.  :smileyvery-happy:   I’m so sorry, I couldn’t resist.  I would download our DLG Diagnostics tool, and see if you can use it to write zeros to the drive.  If the drive hasn’t been firmware damaged, this will restore it to it’s pre-initialized state and you can use your Windows 7 disk to format and install 7 back onto the drive.

DLG Diagnostics